Electric motors and generators frequently employ radially oriented permanent magnets in their rotors or stators that are alternately magnetized inward and outward. Usually these are assembled from individually manufactured, block magnets arranged in a circle about the rotational axis of the rotor. In more sophisticated configurations the magnetic ring consists of arched circular segments that are fitted together to form an annular ring. Such a configuration is still not ideal, however, because each individual segment has unidirectional magnetization and hence only along its central radius is the magnetization truly radial.
Alternatively, a magnetic ring can generate a nearly radial magnetic field by making the angular width of the individual segments relatively small. This involves much individual magnetization and assembly and is usually not cost effective or convenient. On the other hand if one-piece magnetization of the entire ring is done, the strength of the magnetic field around the ring is very small if the magnetization is attempted by traditional means, especially in rings of short period where adjacent magnets tend to cancel each other's fields and where the necessary magnetizing field strengths are difficult to obtain, again because of mutual cancellation of adjacent magnetizers. This problem could be overcome by using a stronger magnetizing field, but this is as hard to affect as is the magnetization itself.
The purpose of this invention is to obtain much greater field strength in a one-piece periodic ring magnetizer than is traditionally available. Very high radial fields are available from two northern or two southern hemispheres of a magic sphere joined at their equatorial planes. In the former case the radial field at the equator is outwardly directed and in the former case inwardly directed.